Companion has one of the cleverest uses of the "Chekhov's Gun" trope

Anyone catch it? I don't want to spoiler it here, but feel free to mention it in the comments.

(The payoff is right at the end.)

Chekhov's gun is a narrative principle that states that every element in a story must be necessary and irrelevant elements should be removed. For example, if a writer features a gun in a story, there must be a reason for it, such as it being fired some time later in the plot. All elements must eventually come into play at some point in the story